Spray forming of FeSi{sub}2 thermoelectric device by controlled-atmosphere plasma spraying

摘要

To fabricate large size thermoelectric power generator device, spray forming of β type iron disilicides (FeSi{sub}2) doped with 2 at% and 5 at% Co was conducted by using controlled-atmosphere plasma spraying system (CAPS) filled with argon under the pressure ranging from reduced (6 and 50 kpa) to nearly ambient pressure (115 kpa). The effect of thermal spray conditions on relative density and spray efficiency was studied. Under the pressure of 6 kPa, both the relative density and spray efficiency increased with increasing plasma power. When the plasma power was 42 kPa the relative density decreased with increasing chamber pressure from 6 kPa up to 115 kPa, on account of fine cracks due to super-heating of the formed silicide. These results suggest that the temperature control is critical for producing crack-flee device. By fixing spray distance at 300 mm and Ar blow cooling, two types of large size FeSi{sub}2 thermoelectric devices, one is a plate-type with the size of 100 mm square and the thickness of 5 mm and another is a tube-type with the length of 300 mm and the thickness of 3 mm, were successfully spray-formed without any macro crack.